


how do you want this?

by Bootsrcool



Series: The Harry Potter/UnderTale crossover that nobuddie asked for [15]
Category: Harry Potter - J. K. Rowling, Undertale (Video Game)
Genre: Anal Fingering, Anal Sex, Harry Potter and the Bonezone, IT IS HERE, M/M, ectodong, the dong is here, told ya it would happen
Language: English
Status: Completed
Published: 2018-02-02
Updated: 2018-02-02
Packaged: 2019-03-12 14:39:48
Rating: Explicit
Warnings: No Archive Warnings Apply, Underage
Chapters: 1
Words: 2,076
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/13549461
Author URL: https://archiveofourown.org/users/Bootsrcool/pseuds/Bootsrcool
Summary: Like this?





	how do you want this?

**Author's Note:**

> So! This happened! Happy Xmas, New year, halloween, easter, whatever holidays went by since the last time I posted.
> 
> I really dont know when the next stuff will be out. Undertale and the fandom took its first break from my mind in two years a few months ago + real life hates me. Ive moved three times in the last 6 months and another move may be coming up in the future.
> 
> Also! Sherlock! and LOTR and Bagginsheild and Johnlock!!! Other fandoms have breaeched my fandom kingdom!!! And with every fandom, there is a hp crossover to read. So yeah. How are you all doing?
> 
> I have a new link in the end notes that isnt my tumblr. Feel free to check it out. Maybe press the button it leads to? Would really help me out!
> 
> Love you guys and sorry for playing dead! I didnt mean for it to go on this long! Hopefully this will snap me out of my writers and undertale block! ^.^
> 
> Lots of love,
> 
> Boots!
> 
> EDIT 02/03/18: Revamped it so it runs more smoothly and has more descriptions in it. Still not used to writing smut though. sorry!

Sans couldn't believe how this run was going. The kid hadn't shown up in Snowdin for so long. A different human had fallen down and the skeleton would think anyone who suggested him falling for a human would have been met with a laughing skeleton before seeing what the inside of a Gaster Blaster looked like.

He was so shocked when instead of the little kid who could wipe out the monsters in a few short days one run or befriend all of the monsters in another, there was this teen whose soul just shined. He went through the script for the most part. The new human played along with Paps, doing the puzzles, staying at the brothers house…..Then he brought dad back. Sans couldn't say how much he worked on that machine, trying everything he could to get Gaster out of the void, and the human, Harry, just waved a stick around and muttered a word and bam! There’s the long lost father of the skelebros. And Sans was embarrassed to admit it, but he was already falling for Harry before that miracle had even happened.

When Harry told Sans about the war that he was the center of, Sans was so upset on behalf of Harry. While the Humans had left them down here to probably die, the monsters never had wars between themselves. It probably helped that there has only been one sole ruler since the War, but there were not many monsters who took their anger out on others of the monarchy. Yes, lots of monsters were unsatisfied about being trapped, but monsters persevered. It's who they are.

So Sans promised himself, that night with Harry sleeping in his arms. He would do whatever it took to see not only Harry coming out of what awaited them on the surface, he would bring Justice to those responsible for setting a young child up in a war. For making them think they had no other option.

For a moment, Sans thought back to Frisk, who were nice the first few runs, when trying to free them. Maybe they thought they had no other option too?

 

Sans also thought back to when Harry made his promise of getting monsters out. To see the sun and stars with Papyrus and Sans. Now that there was a sliver of hope, Sans couldn’t wait to see Harry gaze upon the stars.

The walk through Waterfall was entertaining and a breath of fresh air for Sans, who hasn't taken the time like he did with Harry before. Sure, he enjoyed leisure walks around the caves and he sometimes sat down at the water's edge, thinking usually not pleasant thoughts, but he would also think of times from before. Before Frisk, before Gaster, back when the family was together and were happy. Content. He was content now, with Harry.

Harry, who was currently straddling his femers, kissing Sans like he was a water cooler in Hotland.

*****

Harry was very proud of the way he made Sans’ whole face light up blue, eye lights forming into little hazy white hearts. He was shocked for a moment when he felt a tongue touch his own back when he licked Sans teeth. After that, he dived right in. He couldn't help but devour Sans, his building lust spilling over. He was so happy. Sans wanted him and he wanted Sans and was this feeling he had in his chest love? He had the feeling of completion that was so foreign to him. The closest he felt to this was when he was with Hedwig up in the astronomy tower or owlery at Hogwarts. He was just overtaken with a calm wave of contentedness. 

Sans sighed into Harry and leaned back, arms working their way behind the teen and pressing down on his shoulder blades so Harry would fall on top of him. For a while that stayed like that, Sans on his back with Harry on top, having the best snogging session of their lives. Then their hands started to wander further than just shoulders and back. Sans hand suddenly found itself on the top of Harry’s ass, a finger dipping into the crease and Harry moaned like he did that time he was eating Papyrus’ pancakes. Sans other hand gripped the sheets, holding tight.

Harry’s hand slid down from Sans’ shoulder, down breastbone and grabbing onto his ribs. the other hand grabbing the back of the skeletons skull. At the grip, slick with sweat, Sans let out a groan of his own and thrust up into Harry, making something very noticeable to the human.

“Oh fuck.”

Sans licked and nipped down Harry’s neck. “only if you want to.” He said, tugging questioningly at Harry’s plain grey/blue shirt. Harry pulled apart long enough to pull it off and throw it to the floor.

“Oh god, I want!” Harry said before leaning down and licking a long, broad strip from the bottom of his breastbone to the clavicle, giving a nip of his own. Sans let out a shocked yell, raising a hand to muffle the sound before Harry stopped it and grabbed the bones, twining his fingers with the phanangles. “I want to hear you.” Harry said, looking up shyly from where his head was resting against Sans shoulder. Sans smiled and flipped them over so he was on top before peeling off his shirt and throwing it behind him. Harry reached down and fiddled with Sans shorts, looking up at him curiously. Sans flushed a very saturated blue and nodded, watching as the teen pulled at the strings keeping the shorts on and sliding them down Sans legs, freeing his dick. Which was glowing blue. His favorite shade of blue. It was also about the same size as Harry’s own seven and a quarter inches. Where Harry had an average girth, Sans was wider. And glowing.

Harry stared at it before leaning over and giving it a lick. He had never given or received a blowjob before, but it couldn't be that hard. Worth a try though.

With that thought and at the pleasure filled moan Sans let out, Harry took the head into his mouth and sucked.

Sans was dead. He was borderline close to cumming and Harry had his cute mouth wrapped around his cock. “fuuuuuucckkk.”

Harry pulled back with a pop. “Good?” He asked uncertainty.

Sans nodded and continued nodding as Harry went back down, taking more of Sans dick into his mouth. “so good.”

Harry sucked and pressed his tongue against the thick vein on the bottom and Sans had to pull away at that. “sorry!” The monster gasped, trying to catch his breath. “was gonna cum.”

Harry grinned at that. “Really?” At Sans nod, Harry beamed up at the skeleton before laying back down and wiggling out of his jeans. “You said you wanted to fuck me?”

“yes.” Sans growled, crawling over the teen before pausing. Reaching over to the bedside table, Sans pulled the drawer open and grabbed a bottle of lube. “oh, good. mettaton still keeps lube in the rooms.”

Harry snorted in laughter. Leave it to the seemingly sex starved robot to keep his hotels rooms stalked with lube. The laughter trailed off as Sans poured a generous amount of the slick on his fingers, spreading them about to cause friction to heat it up. Sans looked over at Harry and coughed a little. 

“how, uh, how do you want this? i mean, i know the theory and all, but how would you prefer to lay, or be positioned? uh…”

Sans trailed off and Harry smiled, leaning up and pulling Sans on top of him. “Like this. Facing you.” Sans blush, which had not completely diminished, flared back up with a vengeance. Harry thought it was both the most hot and adorable thing ever.

“ok. lay back for me? with your legs like…” Sans coaxed Harry's legs up and towards his chest. “...this..”

Harry nodded, grabbing his knees and keeping them tucked towards his chest. Sans let out a shaky breath before reaching down to where he could see Harry’s opening. He slowly circled a finger around the pucker, massaging it to relax the muscles. When he physically felt Harry relax into the touch, Sans pushed the finger in.

“Wow. Whoa.” Harry let out a breath as he felt the warm bone sink into him. It was odd. Not like how he had imagined literal bone to feel, but then again it was Sans. A skeleton monster, not an actual skeleton.

“good? okay?” Sans asked staring at the teens face. Harry nodded. 

“Great. Just odd.”

“do you want me to stop?”

“No! Please keep going?”

Sans nodded, looking down at where his finger was inside of Harry. Sans moved it abit, rubbing the inside some before going for a second finger. Harry let out a small hiss at the pressure before it morphed into a groan of somepain but morepleasure when the phalanges brushed against wat must be his prostate. Seeing Sans hesitating, Harry thrusted back to impale himself more.

“oh stars.” Sans muttered, gently pulling his fingers out most of the way before pressing back in. “this might be my dick.”

“It's going to be your dick, bonehead. Unless you don't stop teasing and stretch me already.” Harry moaned as Sans spent a while thrusting into him instead of stretching him.

Sans moaned at the confirmation that the tightness around his fingers will soon be around his cock. He set to finish stretching Harry, scissoring his fingers and adding a third one, keeping up the stretching longer than was perhaps necessary, but Sans didn't want to hurt Harry, so the teen would just have to wait an extra few minutes.

When he was done, he pulled his fingers out carefully and grabbed the lube again, slicking his cock and giving the base a squeeze to stave off an early climax. “you ready?

Harry nodded, flushed rede down to his chest. “Yes! God, please, get inside of me.” Sans positioned himself with one hand, the over grasping at Harry’s hip.

“you can call me sans,” The skeleton replied before pushing the tip of his dick against the hole and pushing in.

For a moment no sound was heard but the squelch of lube on skin as Sans sunk halfway into Harry’s body. Then a shaky exhale escaped Sans and Harry let out a loud and lewd moan, clenching his hands under his knees harder til his knuckles started turning white. Sans looked down where his cock was still slowly making its way inside of Harry. “holy shit.”

“Sans, Move!” Harry suddenly said before grabbing Sans around the neck and pulling his bonehead down for a kiss. At the movement, Sans just, fell into Harry, bottoming out and muffling a yell into the teens mouth. When they parted, Sans looked down at the human.

“are you alright?”

“Yes!” Harry moaned in response. “Move? Please?”

Sans nodded breathlessly as he pulled out halfway before thrusting back in. He kept doing that, pulling out further and sinking back in more deeply and strongly. Soon enough a rhythm was made and Harry thrusted back when Sans was entering him.

“Close,” Harry warned with a gasp. Sans grunted as he shoved himself into the teen a few more times before warning with a strangled cry, reaching between them to stroke at Harry’s prick. 

“gonna cum….” 

A few strokes were all it took for Harry to start spilling over, cum leaking over Sans hand. At the sensation of cum on his hand, Harrys dick pulsing in said hand and Harry’s ass clamping down tight around Sans, the monster was lost in the pleasure as he shot inside of his human, arms trembling with holding him up above the teen.

When the tingling in his ass started, Harry opened his eyes to stare up at Sans. His eye sockets were clenched tight in bliss before they opened to reveal hazy lights that slowly came into focus on Harry’s face. They stared at each other, smiling, before Sans gently pulled out and rolled over so he wouldn't crush him. 

They laid in silence, staring at each other for a few minutes before they both smiled at each other.

“Shower?” Harry asked. Sans nodded and heaved himself up to a sitting position before falling back down.

“shower. as soon as i can feel anything below my waist.”

Harry smiled. “Ditto.”

**Author's Note:**

> https://ko-fi.com/S6S16IZT
> 
> come visit me and my shit blog thingy at bootsrcool.tumblr.com


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